As told by staff of SPCC, casual wear is fine for both Science Workshop and O Day. There is also no special requirement for student photo -- just make sure that he/she wears the school badge.
more news, SPCC just called me (9: 05 pm) to confirm the cancellation of 25/8's O day, and i asked her the dressing code again on science workshop and she said someone will call me again.... so have to wait again